This invention relates to a lead acid storage battery and especially to a sealed-type lead acid storage battery.
A general lead acid storage battery has so far been made by inserting assembled plate groups into a container and bonding a cover onto the container. The container has generally been made by forming and working synthetic resin into a boxed shape. In this lead acid storage battery, adjoining cells have generally been connected to each other by a connecting conductor installed on top of a partition wall of the container. In this lead acid storage battery, however, the container has had to be made by fabricating an expensive metal mold for every change in battery size resulting in high cost and low productivity. Further, there have been problems such as increases in weight, volume and electrical resistance of connecting parts of cells.
On the other hand, a demand for a sealed-type lead acid storage battery with high energy density has been increasing in recent years, and a mono-block-type sealed-type lead acid storage battery is proposed as disclosed, for example, in Published Japanese Patent Application (KOKAI) no. 62-80973. This lead acid storage battery is fabricated by joining two half containers 100 opposing each other as illustrated in FIG. 12. The half container 100 contains three cells 101, 102 & 103 as illustrated in FIG. 13. As for the adjoining cells 101 & 102, a positive current collector 104 is connected to a negative current collector 105 by a connecting conductor 106. The connecting conductor 106 pierces through a partition wall 107. Since the cells are connected to each other at a middle part of the current collectors in this lead acid storage battery, it has features such as (i) the electrical resistance becomes small, and (ii) the weight and volume of the connecting conductor can be reduced as compared with a case where plate lugs are connected each other. However, there have been the following problems (1) to (4):
(1) A process for integrally molding the half container to the current collector, is required. PA1 (2) A process for bonding the half containers to each other, is required. PA1 (3) Since the current collectors are buried in the half containers, heat releasing ability is bad so that a battery temperature is apt to rise.
(4) It is difficult to fabricate the cells by using three or more plates.